Relative Dating and Correlation
1. Connect the strata in that are the same age.
2. Describe the geological history in outcrop 3 beginning with layer D.
3. Which of the following is the most likely age for the
conglomerate?
A. late part of the Tertiary
B. middle part of the Tertiary
C. early part of the Tertiary
D. Pleistocene
The geologic cross section below shows the geologic age of two rock layers separated
by an unconformity.
4. The unconformity at the bottom of the Silurian rock layer indicates a gap in the
geologic time record. What is the minimum time shown by the gap?
Use the following information to answer the next two questions.
Fossilized Jellyfish Found in Wisconsin
Fossil hunters have unearthed the largest collection of fossilized jellyfish ever
discovered, including the largest fossilized jellyfish ever found. The remains of softbodied animals such as jellyfish are relatively rare because they don’t have bones, fossil
dealer Dan Damrow, James W. Hagadorn of the California Institute of Technology and
Robert H. Dott Jr. of the University of Wisconsin at Madison noted in describing the find
in the journal Geology.
About a half-billion years ago, during the Cambrian period, the quarry in Mosinee,
Wis., where the deposits were found was a small lagoon. The jellyfish apparently died
when they were washed up by a freak tide or storm, the researchers said. The jellyfish
remains were probably preserved because of a lack of erosion from sea water and wind,
and a lack of scavengers, the researchers concluded. “It is very rare to discover a
deposit which contains an entire stranding event of jellyfish,” Hagadorn said. “These
jellyfish are not just large for the Cambrian, but are the largest jellyfish in the entire fossil
record.”
Washington Post, January 2002
4. These fossilized jellyfish were most likely discovered in which type of rock?
a. sandstone
b. pumice
c. granite
d. slate
5. Which evidence would lead scientists to suspect that a tide or storm had washed
up these jellyfish on a beach?
a. Primitive life existed on land 500 million years ago.
b. The rock containing the jellyfish fossils has distorted crystal structure.
c. Treeroot fossils appear to have been pitted and folded.
d. Large ripple marks were found in the fossil-containing rock layers.